The field of the present invention relates generally to apparatus for protection against an accidental sharps injury or stick from an unprotected needle.
For some time, the art has recognized the desirability of protecting personnel from accidental sharps injuries or needle sticks. More recently, concerns have been expressed about the possibility of transmitting serious or potentially fatal infection as a result of such accidents. Most recently, legislation requiring the use of safe needle technology is pending in a number of States and before the Occupation Safety and Health Administration. Although, the art has recognized the desirability of protecting against accidental sharps injuries or needle sticks, it is believed that practical protective devices are still not available.
U.S. Pat. No. 5,209,739 discloses a hypodermic needle assembly and a syringe, both having a retractable cannula. An elastomeric tube is connected between the cannula and the passage to the fluid chamber. In each of the embodiments, a separate mechanical device must be independently operated by the user to cause retraction of the cannula into a second compartment. Since the fluid must travel through the elastomeric tube to bypass the second compartment, there is a potential risk of injecting air directly into the patient if the elastomeric tube breaks.
European Patent No. 0 862 A1 discloses a device in which a needle is retracted into the syringe. In several of the embodiments, the device requires the user to independently operate a mechanical device to cause retraction of the needle. In the one embodiment which utilizes an elastic member, the elastic member is not preloaded and requires the user to depress the plunger to load the elastic member and thereafter continue to apply pressure on the plunger to avoid premature withdrawal of the plunger. As such, the device requires two hands for its operation.
Various methods of providing a preloaded retraction assembly which permit one hand operation are disclosed in co-owned PCT Application No. PCT/US97/20646, International Publication No. WO 98/20923. While these devices operate successfully, it has been found that the devices may have a somewhat reduced shelf life since the retraction member remains in a tensioned, preloaded condition.
Other devices which allow the retraction member to be loaded by the user have been introduced. However, these devices generally require a complicated or non-routine procedure to accomplish such. The further a device is from routine operation, the generally less accepted it is by the medical community. Additionally, some of these devices require a mechanical altering of the device which may be difficult to accomplish or may cause deformities which prevent the device from operating properly. See for example U.S. Pat. Nos. 5,928,200 and 5,836,917.
Furthermore, many retractable systems employ a geometrically configured retraction member which mates with a geometrically configured member of the needle assembly. A common problem associated with such is the geometrically configured retraction member is forward of the plunger sealing surface and thereby engages and seals the passageway through the needle assembly before all of the fluid is expelled. As a result, pressure builds in the syringe body. As the needle assembly retracts, a fluid passage opens and the pressurized fluid is ejected therefrom.
Another concern with prior art devices is the complicated and costly manufacturing processes. With the tremendous number of syringes and other needle devices used by the medical community, any substantial rise in cost of the products is undesirable and generally unacceptable.
Accordingly, there is a need for a syringe having an automatically retracted used needle assembly that can be used in a conventional manner and does not require elaborate manufacturing.